Hiyas,
the naming guidelines say that one should use the date do describe the snapshot:
http://fedoraproject.org/wiki/Packaging/NamingGuidelines#head-cfd71146dbb6f0...
| If a snapshot package is considered a "pre-release package", you should | follow the guidelines listed in Pre-Release Packages, and use an %{alphatag} | in the following format: | YYYYMMDDcvs
Maybe this is useful for cvs, because there is no better way to describe a snapshot. But e.g. with svn, which uses a global revision number, it is possible to use a unique id for the snapshot, where it is not uncertain which changes are included. For this reason I suggest to change the guideline, so that it suggests better identification strings for a snapshot, when it is avaiable, e.g.
123svn
for a snapshot of an svn repository at revision 123.
Regards, Till